Hi Brent and welcome. No Sir as you would need a different upper or slide between 9mm and .45acp. Caliber and firearm make a difference. For example, I shoot 4 different calibers out of my Glock Model 20 with just a barrel change - 10mm - .40S&W - .357Sig - 9x25 Dillon. Cheers and stay safe!

Brent, depends on the firearm but most likely no. Some firearms will allow you to switch calibers by swapping barrels/slides but 45acp and 9mm are different enough that not alot of firearms are able to. If you have a firearm in mind just post again with the model number or upc and we can give a definite answer. You can find the model number and upc under the products description. Hope this helps.